Cartridge shells are sometimes used as activators for other devices, e.g. to release a projectile terminated by a knife edge so as to cut a lanyard and release a payload thethered to the lanyard. Such a cartridge shell may typically have a casing with the projectile attached thereto, with the casing having a central opening in which is disposed an explosive charge to fire the projectile, and a fuse to transmit ignition from a primer cap to the explosive charge. The length and composition of the fuse determines what delay occurs between firing of the cap and ignition of the charge, and the mechanism by which the projectile attaches to the cartridge determines at what gas pressure within the cartridge causes release of the projectile. A delay between firing the primer and launching the projectile is advantageous for the systematic deployment of an applicable systems or payloads. In this manner, the burn time of the fuse determines the delay time between firing of the cartridge and the release of the projectile. Assembling the fuse at the proper length, however, can be difficult. To do so, one typically forms a portion of the cartridge's central opening into a ledge, and forms the fuse by stacking chemical energetics into the central opening up to the ledge. In practice, it is difficult to determine precisely how closely the height of the energetics stack registers with the ledge, requiring extra manufacturing steps to verify fuse position before fixing the fuse in place, for example by adhesive.
Also, at the opposite end of the fuse near the explosive charge, the casing has another ledge upon which rests and physically supports the fuse. This means that the fuse is not fully supported at its base, which gives rise to shearing forces and bending moments that can fracture the fuse, and cause failure of the cartridge.